The present invention relates to structures that protect organic optoelectronic devices from species in the surrounding environment.
Organic optoelectronic devices, including circuits, such as organic light emitting diodes, organic electrochromic displays, organic photovoltaic devices and organic thin film transistors, are known in the art and are becoming increasingly important from an economic standpoint.
As a specific example, organic light emitting devices (xe2x80x9cOLEDsxe2x80x9d), including both polymer and small-molecule OLEDs, are potential candidates for a great variety of virtual- and direct-view type displays, such as lap-top computers, televisions, digital watches, telephones, pagers, cellular telephones, calculators and the like. Unlike inorganic semiconductor light emitting devices, organic light emitting devices are generally simple and relatively easy and inexpensive to fabricate. Also, OLEDs readily lend themselves to applications requiring a wide variety of colors and to applications that concern large-area devices. In general, two-dimensional OLED arrays for imaging applications are known in the art and are typically composed of a plurality of OLEDs (one or more of which forms a pixel) arranged in rows and columns. Each individual OLED in the array is typically constructed with a first transparent anode (such as ITO), an organic electroluminescent layer on the first electrode, and a metallic cathode on the organic electroluminescent medium. Other OLED architectures are also known in the art such as transparent OLEDs (transparent cathode contact), and inverted OLEDs. Substrate materials may include glass, plastic, metal foil, silicon wafers, and so forth.
In forming an OLED, a layer of reactive metal is typically utilized as the cathode to ensure efficient electron injection and low operating voltages. However, reactive metals and their interface with the organic material are susceptible to oxygen and moisture, which can severely limit the lifetime of the devices. Moisture and oxygen are also known to produce other deleterious effects. For example, moisture and oxygen are known to increase xe2x80x9cdark spot areasxe2x80x9d in connection with OLEDs. Components of various other organic optoelectronic devices (e.g., organic electrochromic displays, organic photovoltaic devices and organic thin film transistors) are likewise susceptible to attack from exterior environmental species, including water and oxygen.
The above and other challenges are addressed by the present invention. According to an embodiment of the present invention, an organic optoelectronic device structure is provided which comprises the following: (a) a polymer substrate layer; (b) a first barrier region, which comprises two or more planarizing layers and two or more high-density layers, disposed over the polymer substrate layer; (c) a second barrier region, which comprises two or more planarizing layers, two or more high-density layers and at least one layer of an absorbing material that absorbs water, oxygen or both water and oxygen, disposed over the first barrier region; and (d) an organic optoelectronic device, which is selected from an organic light emitting diode, an organic electrochromic display, an organic photovoltaic device and an organic thin film transistor, disposed between the first and second barrier regions. The first and second barrier regions in this structure restrict transmission of water and oxygen from an outer environment to the optoelectronic device.
According to another embodiment, an organic optoelectronic device structure is provided that comprises the following: (a) a first barrier region; (b) a second barrier region; and (c) an organic optoelectronic device, which is selected from an organic light emitting diode, an organic electrochromic display, an organic photovoltaic device and an organic thin film transistor, disposed between the first barrier region and the second barrier region. In this structure, the first and second barrier regions restrict transmission of water and oxygen from an outer environment to the optoelectronic device. Moreover, at least one of the first and second barrier regions comprises the following: at least two planarizing layers, at least two high-density layers, and at least one layer of a material that absorbs water, oxygen or both water and oxygen.
According to another embodiment of the present invention, an OLED structure is provided that comprises: (a) a polymer substrate layer; (b) a first barrier region disposed over the polymer substrate layer, which comprises two or more planarizing layers and two or more high-density layers; (c) a second barrier region disposed over the first barrier region, which comprises two or more planarizing layers, two or more high-density layers, and at least one layer of an absorbing material that absorbs water, oxygen or both water and oxygen; and (d) an OLED disposed between the first and second barrier regions. The first and second barrier regions in this structure restrict transmission of water and oxygen from an outer environment to the optoelectronic device.
In each of the above embodiments, the layer of absorbing material preferably comprises an alkaline earth metal, more preferably, calcium metal and/or barium metal, which is preferably grown under vacuum conditions.
Each of the first and second barrier regions preferably comprises three or more planarizing layers and three or more high-density layers.
Each of the first and second barrier regions also preferably comprises multiple layer pairs, wherein each layer pair consists of a planarizing layer adjacent a high-density layer. The layer of absorbing material can be disposed between two of these layer pairs.
In some embodiments, the first barrier region further comprises a layer of absorbing material that absorbs water, oxygen or both water and oxygen. In some instances, the layer of material that absorbs water, oxygen or both water and oxygen can be placed adjacent the polymer substrate layer.
In some embodiments, the first and/or second barrier region comprises at least three planarizing layers in an alternating series with at least three other layers. The at least three other layers in these embodiments comprise at least two high-density layers and at least one layer of material that absorbs water, oxygen or both water and oxygen.
In other embodiments, the first and/or second barrier region comprises at least three high-density layers in an alternating series with at least three other layers. The at least three other layers in these embodiments comprise at least two planarizing layers and at least one layer of material that absorbs water, oxygen or both water and oxygen.
One advantage of the present invention is that organic optoelectronic structures are produced that are protected by an effective barrier between the organic optoelectronic device and the ambient atmosphere, reducing the adverse effects of chemical species in the ambient atmosphere, such as moisture and oxygen.
Another advantage of the present invention is that organic optoelectronic devices can be encapsulated within a multilayered structure. Such structures are advantageous, for example, in that they lend themselves to continuous processing techniques, such as web-based manufacturing methods, in that they are typically flexible and conformable to other surfaces, and in that they typically permit transmission of light.
These and other embodiments and advantages of the present invention will become readily apparent to those of ordinary skill in the art upon review of the disclosure to follow.